java实现RC4加解密

一.前言

在密码学中，RC4是一种流加密算法，密钥长度可变。它加解密使用相同的密钥，因此也属于对称加密算法。

二.示例代码

import java.io.UnsupportedEncodingException;

public class RC4Util {
 
	public static String encryRC4String(String data, String key,String chartSet) throws UnsupportedEncodingException {
		if (data == null || key == null) {
			return null;
		}
		return toHexString(asString(encryRC4Byte(data, key,chartSet)));
	}
 
	public static byte[] encryRC4Byte(String data, String key,String chartSet) throws UnsupportedEncodingException {
		if (data == null || key == null) {
			return null;
		}
		if(chartSet==null||chartSet.isEmpty()) {
			byte bData[] = data.getBytes();
			return RC4Base(bData, key);
		}else {
			byte bData[] = data.getBytes(chartSet);
			return RC4Base(bData, key);
		}
		
	}
 
	public static String decryRC4(String data, String key) {
		if (data == null || key == null) {
			return null;
		}
		return new String(RC4Base(HexString2Bytes(data), key));
	}
 
	public static String decryRC4(byte[] data, String key) {
		if (data == null || key == null) {
			return null;
		}
		return asString(RC4Base(data, key));
	}
 
	private static String asString(byte[] buf) {
		StringBuffer strbuf = new StringBuffer(buf.length);
		for (int i = 0; i < buf.length; i++) {
			strbuf.append((char) buf[i]);
		}
		return strbuf.toString();
	}

	private static byte[] initKey(String aKey) {
		byte[] bkey = aKey.getBytes();
		byte state[] = new byte[256];
 
		for (int i = 0; i < 256; i++) {
			state[i] = (byte) i;
		}
		int index1 = 0;
		int index2 = 0;
		if (bkey == null || bkey.length == 0) {
			return null;
		}
		for (int i = 0; i < 256; i++) {
			index2 = ((bkey[index1] & 0xff) + (state[i] & 0xff) + index2) & 0xff;
			byte tmp = state[i];
			state[i] = state[index2];
			state[index2] = tmp;
			index1 = (index1 + 1) % bkey.length;
		}
		return state;
	}
 
	private static String toHexString(String s) {
		String str = "";
		for (int i = 0; i < s.length(); i++) {
			int ch = (int) s.charAt(i);
			String s4 = Integer.toHexString(ch & 0xFF);
			if (s4.length() == 1) {
				s4 = '0' + s4;
			}
			str = str + s4;
		}
		return str;// 0x表示十六进制
	}
 
	private static byte[] HexString2Bytes(String src) {
		int size = src.length();
		byte[] ret = new byte[size / 2];
		byte[] tmp = src.getBytes();
		for (int i = 0; i < size / 2; i++) {
			ret[i] = uniteBytes(tmp[i * 2], tmp[i * 2 + 1]);
		}
		return ret;
	}
 
	private static byte uniteBytes(byte src0, byte src1) {
		char _b0 = (char) Byte.decode("0x" + new String(new byte[] { src0 })).byteValue();
		_b0 = (char) (_b0 << 4);
		char _b1 = (char) Byte.decode("0x" + new String(new byte[] { src1 })).byteValue();
		byte ret = (byte) (_b0 ^ _b1);
		return ret;
	}
 
	private static byte[] RC4Base(byte[] input, String mKkey) {
		int x = 0;
		int y = 0;
		byte key[] = initKey(mKkey);
		int xorIndex;
		byte[] result = new byte[input.length];
 
		for (int i = 0; i < input.length; i++) {
			x = (x + 1) & 0xff;
			y = ((key[x] & 0xff) + y) & 0xff;
			byte tmp = key[x];
			key[x] = key[y];
			key[y] = tmp;
			xorIndex = ((key[x] & 0xff) + (key[y] & 0xff)) & 0xff;
			result[i] = (byte) (input[i] ^ key[xorIndex]);
		}
		return result;
	}
}

三.测试代码

String encryStr = RC4Util.encryRC4String("测试", "123456","UTF-8");
System.out.println("加密后得到得字符串："+encryStr);
String decryStr = RC4Util.decryRC4(encryStr, "123456");
System.out.println("解密后得到得字符串："+decryStr);

四.运行结果

加密后得到得字符串：e64df58f8ba6
解密后得到得字符串：测试